1. Field of the Invention
The present invention relates to a method of scrambling PAL, SECAM and NTSC composite video signals and to a decoder of signals scrambled by this method.
2. Discussions of the Background
A large number of methods are known for scrambling the video signals of television images in a pay television system. Among these methods there is known a method of scrambling by circular on-line permutation. This known method, while allowing a scrambling of the image, is not a priori shielded from any "pirating" because of certain temporal characteristics of the scrambled signal which are easy to locate.